SW2UZ

iTrader: (3)

92 sc400

I'm at my wits end here, I have been trying to diagnose this random sputtering/bogging/missfire issue that I have had for the last 2 weeks.

So about 2 weeks ago I ran really low on gas I only had about 2 bucks in change (left the wallet at home) stopped off at a shell station put in 87 and started heading home, I got about 1/2 mile then the car started sputtering missing real bad, bad gas? thats what I thought fast forward two weeks and I still have this intermittent issue with bogging/stuttering and random missing that goes away then comes back when it wants to.

No Cel, problem seems to increase in frequency when the car is at running temp and gets bad in stop and go traffic
Things that I have checked (I'm broke atm so its DIY diagnostics)
coils
caps/rotors
plugs/wires
ignitors
iac
tps
afm
12v mod no difference (side note you don't need to hack the wires to do mod since car runs with out fuel pump ecu)
fuel filter has less then 500miles

things still to check
injectors
open up ecu/swap with known good one
coolant sensor?
since the issue gets worse the warmer the car is there possibly a connection to coolant temp sensor? or something in the ecu that is about to fail? everything points towards ignition missfire but for the life of me I can't find the cause


took 2 vids sorry for sound quality
the first car is semi cold
http://s552.photobucket.com/albums/j...1217101701.mp4

second operating temp
http://s552.photobucket.com/albums/j...1217101657.mp4

edit: should add that car drives fine one day, then the next problem is back

Thanks for any help/direction you can give me (inb4 use search )

Meanshyguy

iTrader: (11)

Welcome to the club, seems like these cars are notorious for doing this, I've had the same issue almost immediately after I bought the car, and I'm very desperate.
They say it's the ECU, didn't do anything for me, and it probably does it more at normal temp because the spark plug where the missfire is, is already fouled because of so much gas not being burned.
Have you checked the fuel pump?

Let me know what you do and if anything helps cuz I'm on the same damn page.

FatBrian81

iTrader: (2)

My STS started to run oddly about a month or so before the fuel pump died. Rough idle, poor acceleration, general sluggishness, it had them all before the pump went. After a new one it runs great again.

FireCode

iTrader: (1)

Do you smell a strong oder of gas when this happens? Are your cats glowing and pinging like crazy? Obviously, as you know, this means unburnt fuel. Unburnt fuel leads me to belive ignition problmes. Yes I know you checked the coils etc. but there could still be a problem with the components.

Ali SC3

iTrader: (10)

how old are the plugs? how did you check the coils?
a lot of the time sc400 threads like this are ignition related if they are not the fuel pump/12v mod.

willhickey

iTrader: (1)

that guys spot on about the fuel pump.... do you drive on e alot?? it overheats the fuel pump.. the good news are cheap try that and let us know where your at !

Shrugy

iTrader: (12)

I'm having the same issue that you are experiencing. I plan to replace the plugs, and have a shop check out the rest of the vehicle including Coil Pack, and the Fuel Pump.

I hope the repair is a cheap one

oldManTan

this happened to me and went away the next day. i'm subscribing to this in case it happens again. i have a CEL for 25, running lean, and my TRAC and ABS lights are on which is most likely the O2 sensors so i'm waiting for those to come in so i could change them.

Shrugy

iTrader: (12)

Have you got any word on what your issue was?

Is there a way we can eliminate the MAF sensor for being the problem?

I've been told a dirty MAF can cause these issues.